Electrical power measuring apparatus



y 7, 1959 w. H. WANNAMAKER, JR 2,894,207

ELECTRICAL POWER MEASURING APPARATUS Filed July 1. 1954 2 Sheets-Sheet 1 FIG.IY

65 INVEN WILLIAM H. WANNAMA JR.

wx/w ATTORNEY."

July 7, 1959 w. H. WANNAMAKER, JR 2,894,207 ELECTRICAL POWER MEASURING APPARATUS Filed July 1. 195 4 2 Sheets-Sheet 2 9o; FIG. 6

, INVENTOR. WILLIAM H WANNAMAKER JR.

ATTORNEY.

The genera1-object of the present invention is to pr,o vide an improved electrical measuring, apparatus forv measuringtheelectrical conditions of an electrical circuit. More specifically, ,thelpresent invention is concerned with an, electrical measuring apparatus which maybe, used to determinethe power, voltage, andcurrent conditions. of. an. electrical circuit.

In measuring, the.magnitude,- of an electricalflvariablm an: expedient frequently, used, to obtain .highaaccuracy, is to produce, a ,unidirectional voltage tsignalhaving 1a. mag-J nitudetproportioualtothe,measurednvariable. Themeas? ured variable may be voltage, current, power, and the, like; Higheaccuracypf measurernent is possibletbecause the unidirectionahvoltagesignalmaybemeasured'byhigm lyt a :curatempotentiometric measuring means, One, of the problemstinohtainingsueh a, uniditectionalsig'nal that, in power; measurement ,fon, example,. ,the; unidirectional L pqwcmsignahisl,imterms of the product of 'the,..electrical.' circuit,voltage,,,current; and hpowercfactori Heretofore the,apparatust capable of.;makirig ,,sucht product, measure-.1 mentsirlias,,-beenaunduly complex, expensive, and has not: beenaccuratg Tow be usefuhthe product: producing eappagat us mustwbe.,simple, sensitive; andaccurate-oven widerangespflop ration. i

Imaecordance ith thepresentr inventiom, a,yer.y.;eflc-.- tive product producing apparams hasm beenvdevisedaby, utilizingalresistancetuetworlo wherein tthe balahce oi fthe networlsrisrvaried .in accordance rwith the magnitude \ofi one inputwariahle and the energization eithentworklis. varied inizaccordanceswith zthe lmagnitude of fa second Variable With such a network, the [outputs electrical ,signal-iwilltbesa zsignal ,pr oportionalato the product o fi the two, input variables. K i

It -is accordinglp a mo ze specific object of -,=the :present invention to;provide an improved eelectrical measuring apparatusr which includes: a product producing I1tW0Tkt whpse balance is variedain accordanceswith, the. magpi tude ofi n vapiable andathe energization oft the; network edlu izaccordance with-the magnitude.oi, a seconduvariable while the:outputofisaidmetwork is,..inn the formtoffiga uignalt,directly;proportionalito the product ofi,said. variahles-.,-; t p

Another more specific ObjEClL-QfflihGHPIZCSQflt inventionisato pgovidex antelectrical measuring ,apparatus for :meas, urin a variable Hom -an,electrictcircuit wherein saidt apparatus comprises at resistance 1 network, whose :unbals; 6O ance. sis varied inv accordance with, ;a :first electrical .condie tionnoi asaid, circuit, andisaid :network is energized by a. second ielectricalconditiontofsaid circuit Still another, more, specific object of the, present ,in'veni n sl t? RIO iQ n leb l row m a insiapu etus icl di s, a ro u t k n rectifying, nit v as .1 an input theretqfan electromechanical "signal "proppre' tiona'l'to' the voltage" of a'power circuit and Ian-energizing signal proportional";togthe- 'magnitude of tlie-current *of' said-circuit? p p T A till further moie' speeific objeet of thepresent inven a tion is 10* provide an-electr ic circuitWariable measuring nited Sttes Patent 2,894,207 Patented July; 7, 1 959,:

apparatus in the formofaproducttaldng transducer having in its input two separate electrical signals and anoutput proportional: to" the product'of said-signals and, whereinwsaidoutput is connected to atpotentiometric network havingan electrical energizing:sourceincluding-a further electrical signal which maybe variable in accordance with one of the-first mentioned"electrical siga nals.

The various features of 'novelty whichcharacterize the invention are pointed" out with particularity in: the claims-v annexed toand formingapart ofthESPBGlfiGfitlOIL For a better understandingof the invention, its i advantages, and specific objects attained wi'th-its use, reference should behad to the accompanying drawings and descriptive-matter in. which there is illustrated and-describedaipreferred' embodimentof the invention;-

Of the drawings:

Fig. l shows a-schematic arrangement of an 'electrical power measuring: apparatusfor an? alternating current circuitgw Fig. 2 shows one form of resistance typerectifier-used in-the, apparatus in'Fig; 1;

Fig. 3 shows a further type ofresistance rectifier which may be-used in;Fig,- 1; i

Fig, 4-shows a side view of the apparatus shown in Fig, 3; i

Fig. 5 shows the principle of the apparatus applied to a directt-cuprent circuit;-

Fig.5 6? shows a -poly-phase power measuring: circuit in copporating the principleskofil igszl 1 Fig.5 7 showsra further form of rtlre apparatus using' a potentiometric measuring; circuit" energized I by an el'ectrica l rsigna l: derived fromvthe power circuit, andm F Fig. 8 fshows 'amodification of 1tlie electrical circuit of Referring :first to Fig: 1 .thev numerals 10aand= 11 rep= resent electrical leads" for an electrical circuit wherein-it is desired to measure th'ez' power bei-ngsupplie'd'by that 1 circuit: Connected" acrossthe line's 10:ai1d" 11 "'i a-p'o tential transformer 12 shaving a prunary'winding 3 'and a secondary winding 14. The secondary'wihding 14 3s connected-to an energizing coil 15 ofian electro-mechani- CflivtlfillSdLlCBll which converts the elect 'cal input signal supplied thereto into mechanical motion Cooperating with: the coil 15 iare' perrna'nent mag'net poles=16* and' "17 Connected zin 1 series fin the r lin ll is a current "trans former" 20 having a primary winding 21 and-- 'a seco-ndary windingtZZi Connected to be energiz'e d by-the =se'condaryvwinding 22 is a resistance network 25 which mav be inwtheform: ofa Wheatstone bridge type" wherein allot theelementssthereof are variablei The resistanee ele mentsio-f the 'networkareidentified" by the-numerals "26} 2.7,? 8 and29. Connected to the output of the coil 15 inappropriate mechanism 30 for simultaneously varying the magnitudesof'the resistances 215 293 The output of the network 25' is on leads 31 and, 32"

and ihese'leads are connected to aflltersectionSS comprising series'resistors 36; 37 38, and 39"an'dshunting" condensers 4li-and 41. The output ofthe filter '35 con nects to the'input terminals of'a fsuit'able potentiometricmeasuring apparatus 42. This apparatus may take the form-of the apparatus shown in. the -Walter Pi Wills Rater-1t 2,423,540,,issued July 8,-l1947-f As shown, thisapparatus comprises, a potentiomet-ric network '44 re'ceiving its, energization from: a source 45 and-an adjustable potentiometer 46, the latter having a slidewire resistor 47; and;a slider 48: cooperating therewith:

Forfisensing the electrical":unbalance-present in 'th ableltdrivingsignal for -a motor sig" tlidattef ofhvhieh is connected by suitable means 52 to move the slider 48 over the potentiometer slidewire 47.

In considering the operation of Fig. 1, it should first be noted that the coil 15 is energized by an alternating current signal and this will cause the mechanical driving means 30 to be moved in a cyclic manner so as to vary the resistances 26 through 29 in accordance with the magnitude of the applied signal and at a rate which corresponds to the frequency of the applied signal. The mechanical driving means 30 is so associated with the resistors of the network 25 that resistor 26 and resistor 28 are adapted to be decreased in magnitude while the magnitude of the resistors 27 and 29 is increased. With such a balance. variation taking place, the electrical balance of the network25 will be reversing at a rate dependent upon the frequency of the applied signal. In the abscence of an applied voltage to the network 25, there will be no eifective electrical signals on the output leads 31 and 32 even though the balance of the network 25 will be cyclically varying, By applying the electrical signal from the current transformer 20 to the input terminals of the network25, there will be an output signal on the leads 31 and 32. This current signal will be proportional to the current signal flowing in the electrical circuit fed by lines and 11.

The electrical signal of the current transformer will be an alternating current signal and will be of the same fre quency as the signal driving the resistors 26 through 29. By proper connection of the two input signals, the phasing during one half cycle will produce a direct current pulse-on the leads 31 and.32 of a magnitude which is proportional to the voltage signal applied to the coil times the current signal applied to energize the network 25. On the subsequent half cycle, the unbalance of the bridge will be in a direction opposite to that of the first half cycle and the polarity of the applied current signal transformer will also be reversed. As a result, a further direct current pulse of the same polarity will appear upon the terminals 31 and 32. These direct current pulses are effectively filtered by the filter 35 which produces on terminals 55 and 56 a smooth direct current or unidirectional signalwith the ripple due to the rectification being eliminated from the signal. This direct current signal will then be proportional to the product of the input voltage and the current. V

It should be noted that the magnitude of this output voltage will change if, the phase of the current with respect to the voltage in the lines 10 and 11 changes. In other words, the electrical signal supplied by the secondary winding 22 is actually independent of the phase angle or power factor of the lines 10 and 11. However, due to the fact that the coil 15 is energized by the line voltage whose variations may be assumed to be the reference wave, any phase diiference between the applied mechanical signal to the network and the electrical signal to the transformer 20 will result in a decrease of the voltage appearing upon the terminals 55 and 56. Stated in another way, the only current which is effective in this apparatus is the in phase component of the power. This term is conventionally expressed as I cos '0.

The unidirectional signal of the terminals 55 and 56 is applied into the input of the instrument 42 where the voltage is compared with the voltage across the potentiometric network 44. If the voltages across the network 44 are not equal to the voltage across the input terminals 55 and 56, the amplifier 50 will detect the unbalance and drive the motor 51 until such time as the slider 48 is moved to a balance position. The position of the slider may be conveniently calibrated in terms of power being consumed in the electrical circuit including the leads 10 and 11.

From the foregoing it will be seen that the apparatus of Fig. 1 is a. product taking type of apparatus having two separate input variables and an output signal inv terms of a unidirectional signal proportional to the prodnet of the two input variables. It will be readily appar ent that the apparatus of Fig. 1 may be applied in many different ways to obtain the product of preselected input variables.

Referring to Fig. 2, there is shown one form of apparatus for varying the electrical balance of network 25. The apparatus there shown is of a conventional strain gauge type apparatus requiring an input force to produce change in the output of the resistors of the strain gauge.

This apparatus comprises a support member which has attached to the corners thereof the resistors 26, 27, 28, and 29. The resistors project from the corners of the support plate 62 which is a rectangular center piece. This plate is supported by the resistance elements 26 through 29. Extending from the plate 62 is a connecting rod 63 which projects outside of the housing of the apparatus and is adapted to have applied thereto a suitable force. The force producing member in the apparatus of Fig. 2 is an electrodynamic coil 64 which is carried by the rod 63 and is in cooperative relationship with respect to a permanent magnet assembly 65. The alternating current applied to the coil 64 may be the current derived from the potential transformer 12. It will also be readily apparent that the coil 64 may be energized by the current transformer 20. With a cyclic signal applied to the coil 64, the rod 63 will have a cyclically'varying force applied thereto, which force is transmitted to the plate 62. The force on the plate 62 tends to stress the supporting resistors 26 through 29 so that the resistances will be cyclically varied in accordance with the applied signal.

The apparatus of Fig. 3 shows an alternative method of obtaining a cyclically varying mechanical stress of resistors in accordance with an applied alternating current signal, or a direct signal, if such is desired. Here, strain gauge elements 26 through 29 are fastened to a resilient cantilever or reed of a conventional vibrator. Such a vibrator assembly may be of the type shown in the patent of Frederick W. Side, No. 2,423,524, issued July 8, 1947. In this apparatus, the reed 70 is adapted to be'driven by coil 71 which surrounds the upper end 72 of the reed 70. This upper end 72 cooperates with the pole pieces of a suitable permanent magnet identified by the numerals 73 and 74; With an alternating current signal applied to the coil 71, the end 72 will be driven back and forth between the pole members 73 and 74 and in so moving, the reed 70 will be flexed in one direction or the other to strain the resistors 26 through 29 which are bonded thereto. It will be readily apparent that the coil 71 may be energized in any suitable manner by any suitable source of electrical energy.

In Fig. 5, there is shown the apparatus of Fig. 1 7 adapted for direct current power measurement.

' supplied by the voltage derived from the powerlines 81 and 82 by way of leads 83 and 84. The output voltage of this network 25 will be the product of the current flowing in the coil and the voltage across the lines 81 and 82 and there will appear upon the output leads 85 and 86 a signal proportional to that product. It will be readily apparent that the current and voltage connec tions can be reversed in the apparatus shown in Fig. '5 although it will be noted that from the practical standpoint, the current in the lines may be most expeditiously measured by means of a coil rather than by means of a calibrated shunt and an'associated voltage measurement across the shunt. It is to be understood, however, thatthe apparatus is not to be considered limited to the form shown in the drawing of Fig. 5.

Referring now to Fig. 6, there is here shown a poly-Q phasefalternating current circuit wherein it is desired to measure the power to be consumed therein. poly apogee? phase-circuit is represented by'. the power' lines 90, 91, and 9 2*which leadwto a-suitable power-consumingdevice 93. Inw this apparatus, a-first voltagevsignalis derived from the leads "-90 and2 92 by means ofsa potential transformer 94. Anassociatedwcurrentsignal is derivedfrom thealead 92 by a current'transforme'r 95. v qhepotential transformer'94i and the current-trans former 95 are adaptedto energize the product'taking rectifier of'the type shownin Fig. 1 which rectifier bears the same reference-numerals'as 'shown in Fig; 1. In addition,.. a further 1 phase: voltage derived from the linesr90 and 9l=by potentialtransformerf 96. -:A further ncurrentrsignal is derived zfrom the. line'91 by current tnanstormer 97. The potential transformer 96 is: "connected to drivea suitable drivirrgcoil 9&which is the same type of coil as coil 15. This coil in turn operates upon a-further product takingrectifier bridge 99, the latter of which is energized by the current transformer 97.

In the operation of the apparatus of Fig. 6, each of the individual bridge networks :25 and 99 "will "have output'direct current-signalsproportional to -the power conditionsrepresenting the particular phases from which thesignals are derived. These'signals are added in series "bya cireuitthat may betracedfrom the lead 100through the bri'dge' -99, lead-31, bridge -25, and'lead 32 to the filter 35. The-electrical signal "on 'these twobridges equalsthe total power being-consumed in the-circuit fed by leads 90, 91, and 92. The output terminals 55 and 56 may be connected in any desirable manner to the potentiometric measuring apparatus, such as considered with respect to Fig. 1.

Fig. 7 shows a modification of the apparatus wherein it is desired to obtain a measure of the in phase current on the power lines 10 and 11. In this figure, the product taking rectifier section corresponds identically .to that shown in Fig. 1 and corresponding components carry corresponding reference numerals. The modifications in this particular figure are in the potentiometric network in that here the potentiometric network 105 is adapted to have the voltage applied thereto by a bridge type rectifier 106 which is energized by the input power lines 10 and 11. The output of the rectifier 106 passes through a suitable filter 107 and supplies power to the network 105 by way of leads 108 and 109. Since the voltage applied across the potentiometric network 105 is derived from the line voltage on lines 10 and 11, the net effect of this voltage on the potentiometric network is to eliminate the voltage signal derived from the potential transformer 12 so that instead of the apparatus reading EI cos 0, the apparatus will now read only 1 cos 0. In other words, the amplifier 50 will sense any unbalance in the input and adjust the slider of the potentiometer network until the balance point is reached, said balance point being in terms of 1 cos 0.

The apparatus of Fig. 8 shows a further modification of the basic circuit of Fig. 7. In this apparatus, the product taking rectifier corresponds to that of Fig. 1 and Fig. 7 with the exception that instead of energizing the network in accordance with a current signal, the circuit is energized in accordance with the voltage signal from the lines 10: and 11. As a result of this type of enengization, there will appear upon the output leads 31 and 32 a direct current voltage proportional to the product of the two input voltages, or, in other words, E When this circuit is combined with the circuit of Fig. 7 wherein the voltage on the potentiometric network 105 is derived from the line voltage, it will be readily apparent that the voltage applied to the input of the amplifier 50 at balance will be E /E which is, in other words, E. In this form of the apparatus, the apparatus functions as a linear voltmeter.

It will be readily apparent that there are numerous possible modifications in the present apparatus which, under certain conditions, may appear desirable, particularly in the area of reversing the current and potenfal corinections to the electrical circuit undersea-mination.

While, in =accordance with the provisions "of the statutes -th'ere has bemillustrated and described the best forms of the eni'bodirnentsof the invention *known, it will beapparent to those skilled in the art" that changes may be made in tlie' form of theappara'tus disclosedwith out-departing from the spirit of tlie invention as set forth in the appended claims and that in certain cases, certain featuresof' the invention'rnay beuse'd toadvahtag'e Without a corresponding use of-' otherresmr s. 1

Having now described my invention, easel claim as new anddesireto secure by LettersPatent-is:

l. Apparatus for producin aunidirectional signal proportional to alternating current power in an electrical circuit comprising, a first connection to-said cirouitfor providing a first signal I representative or the current "in said circuit, a "second cannection to said circuit -for providing a second signal representative of-the volt-age in said I circuit, -an electro-mechanical device connected by one of said fir'st and second'conriectionsto be energized by the corresponding oneof said first and second signals, and a strain responsive resistance network *having an input and an 1 output adapted to have the I resistors there'- sr anemaiely stressed and strained by i said device in accordance witl'rsaidcorresponding one of said signals, and havin'g -its =input eonneeted by theother of said first and second connections to be energized by the other, corresponding one of said first and second signals such that said network will have an electrical signal on said output that varies in a series of unidirectional electrical pulses of an average magnitude proportional to the magnitude of said alternating current power.

2. Electrical circuit power measuring apparatus comprising, a balanceable strain responsive resistance network having input and output terminals, electromechanical means connected to said network for varying strain on said network and hence the electrical balance of said network in accordance with a signal proportional to the voltage of said circuit, and means for energizing said network in accordance with, a signal proportional to the current of said circuit to produce at said network output a signal proportional to the power of said circuit.

3. Power measuring apparatus for an electrical cirouit comprising, a balanceable electrical network having an input, an output, and network balance varying means comprising an electro-mechanical actuator connected to said network, means connecting one electrical component of said circuit to variably drive said actuator, and circuit means connecting another electrical component of said circuit to said input so that said network will have an output proportional to the product of said components of said electrical circuit.

4. Apparatus as defined in claim 3 wherein said circuit is a poly-phase circuit, wherein said electrical components are the voltage and current of a first phase of said circuit, wherein said output of said network is proportional to the power of said first phase, and wherein there are included a second balanceable electrical network having an input, an output, and network balance varying means comprising a second electro-mechanical actuator connected to said second network, means connecting a third electrical component of said circuit to variably drive said second actuator, circuit means connecting a fourth electrical component of said circuit to said input of said second network to cause the latter to produce an output proportional to the product of said third and fourth electrical components, said third and fourth electrical components being the voltage and current of a second phase of said circuit, whereby said output of said second network is proportional to the power of said second phase, measuring means, and means connecting the outputs of said networks in additive relationship to said measuring means, the latter being responsive to said outputs to provide a measure of the .total power of; said first and secondphases of said circuit.

5. Apparatus as defined in claim 3 wherein there is included-an adjustable potentiometric ,netw'ork'having an output, means connecting one of said electrical components to effectively energize said potentiometric network, whereby the latter produces in its said output ,a balancing signal dependent in value upon the adjustment of said potentiometric network, means interconnecting said outputs of said potentiometric network and said electrical network to oppose saidbalancing signal to said output of said electrical network, and means responsive to a difference between the last mentioned signal and output for adjusting said potentiometric network and hence said balancing signal to reduce said difiercnce.

6. An alternating current electrical circuit power measuring apparatus comprising, a strain type resistance network, electro-mechanical means arranged for con,- nection to said circuit to be energized by an alternating voltage signal representative of the voltage of said circuit, means connecting said electro-mechanical means to mechanically strain said resistance network to vary the balance thereof in accordance with said signal, means arranged for connecting said circuit to said resistance network to energize said resistance network in accordance with a second alternating voltage signal representative of the current in said circuit, said alternating sig- 8 nals having the same frequency, whereby' said resistance network produces .a unidirectional lvoltage output representative of'thepower in said circuit, and'a unidirectional signal measuring means connected to said=L-networkand responsive to saidoutput thereof. I52

7. Apparatus as defined in claim 6 wherein said electromechanical means comprises an electro-dynamic coil and a cooperating permanent magnet. '1

8. Apparatus as defined in claim 6 wherein said electromechanical means is a synchronously driven blade having said strain network formed on the sides thereof.

9. Apparatus as defined in claim 6 wherein said second alternating voltage signal is'the product of the current in said circuit and the cosine of the phase angle between the current and the voltage of said circuit. i

References Cited in the file of this patent UNITED STATES PATENTS Federn Mar. 22, 1955 

